Heterostructures comprised of a 2D emitter and collector separated by a dielectric exhibit resonant tunneling when the band structures of both 2D materials are aligned. It is commonly assumed that the height and width of the resonant peak in the tunneling current are determined by electron scattering and rotational misalignment of the 2D materials. In this article, two fundamental factors limiting the maximum height and steepness of the resonance are identified: coupling to the contacts and tunnel splitting of energy levels. The upper limit of the tunneling current is the number of electrons available for tunneling times half the tunnel coupling between the emitter and collector. As a result of a tradeoff between the contact‐induced level broadening and contact resistance, the maximum current is only achievable when the coupling to the contacts equals the tunnel level splitting. According to model calculations, the limiting behavior can be observed in double‐gated graphene/few‐layer hexagonal boron nitride/graphene heterostructures.
Alymov et al. (Thu,) studied this question.